High temperatures triggered a Bay Area-wide Spare the Air Alert on Friday, but forecasters say the heat won't last.

Mercury readings in parts of San Francisco are expected to reach 74 degrees, with temperatures farther inland in Livermore and Antioch hitting 100 degrees or surpassing it, said Diana Henderson, a National Weather Service forecaster.

Santa Rosa should see temperatures of 88 degrees, while San Jose is expected to peak at 91 degrees and Gilroy at 100.

A combination of the heat and low winds has experts predicting bad air quality throughout the Bay Area on Friday. In the year's seventh Spare the Air Alert, the Bay Area Air Quality Management District asks that residents avoid driving, and warned those with prior respiratory and heart conditions to take extra precautions when outside.

Though the heat is typical of the region's summer season, Henderson said it should break by the time the weekend ends.

San Francisco is expected to be back down to 70 degrees on Sunday, and Santa Rosa to 81 degrees, Henderson said. Temperatures in Livermore are also expected to drop about 10 more degrees and hang at about 90 for the rest of the week.